As a vehicle cruise control device for a vehicle such as an automobile or the like, the following are known: a traveling trajectory control device that controls cruise trajectory so as to causes a vehicle to travel along a target trajectory; and a lane keeping device that determines a lateral dislocation quantity of a vehicle with respect to a lane so as to prevent the vehicle from deviating from the lane. In these cruise control devices, automatic steering control is performed in which steerable wheels are automatically steered by a rudder angle varying device, irrespective of presence/absence of a steering operation by a driver.
In automatic steering control by the cruise control device, information about a situation in front of the vehicle is acquired by an image pickup device such as a CCD camera, a traveling road that the vehicle is to travel along is set based on the acquired image information, and a rudder angle of steerable wheels are controlled so that the vehicle travels along the traveling road thus set. In this case, the setting of a traveling road is executed by electronically processing the acquired image information and determining boundaries of a traveling road such as white lines, guardrails, medians, road shoulders and the like.
In some cases, an image pickup device becomes unable to acquire information about a preliminarily set distance range depending on a driving situation of a vehicle, for example, low visibility caused by fog, disorders of an image pickup device, etc. In such a situation, appropriate cruise control cannot be performed. Therefore, as is described in, for example, JP10(1998)-76965A, an alarm is issued that indicates the stopping of cruise control, cruise control is stopped, and the steering mode shifts from an automatic steering mode to a manual steering mode.
Further, the following is known as well: as is described in, for example, JP2001-22444A, when an image pickup device becomes temporarily unable to appropriately acquire information about a situation in front of the vehicle and cruise control has to be stopped, the vehicle is decelerated so that cruise control should not be stopped and started repeatedly.